Bring a large pan of salted water to the boil. Drop the spaghetti in, pushing it down to submerge it evenly.
Meanwhile, make the sauce: If you are using fresh chile/chilli, chop it very finely; alternatively, use dried flakes. In a large frying pan gently sauté the garlic with the chile/chilli in the olive oil until it is barely golden. Do not let the garlic brown or it will taste bitter. Stir in the parsley. Season with salt and pepper. Remove the sauce from the heat until the pasta is ready.
Remove a mugful of the pasta cooking water and set it aside. Drain the pasta when it is al dente, still with a bite to it. Turn it into the pan with the oil and garlic and cook together over high heat for 2-3 minutes, stirring well to coat the spaghetti with the sauce. If it seems too dry, add a little of the reserved cooking water. Serve at once in a warmed serving bowl, with or without the cheese.